19 Aug 2026
Forests are considered important carbon sinks – but how reliable will they be in a changing climate? A new study shows why land use and changing environmental conditions must be considered together.
Scientists have long known that land use will change substantially in the coming decades, just as rising CO₂ levels and a changing climate will transform the conditions in which ecosystems grow—but surprisingly little research has examined what happens when these changes interact. The new study published in Tellus, co-authored by Julia Pongratz and Clemens Schwingshackl, shows that these interactions are far from a minor detail: changing environmental conditions affect how much carbon is stored in vegetation, while land-use decisions determine which ecosystems will be able to absorb or release carbon in the future.
This matters especially for reforestation, because newly established forests can create additional carbon sinks as they grow and respond to changing environmental conditions, but those same forests may become increasingly vulnerable to drought, heat, fire and other climate impacts. In other words, the carbon benefit expected from planting or restoring forests cannot be assessed independently of the climate those forests will experience.
The study illustrates the growing impact of climate change on ecosystems with the example of 2024, when global warming coincided with El Niño conditions: 25% of the land area acted as a CO₂ source as terrestrial ecosystems were affected by drought and heat, compared with just 9% on average during 2015–2024. Better understanding these land-use–environment interactions will therefore be crucial for determining the future trajectory of atmospheric CO₂ and how reliably reforestation can contribute to future climate targets.